Downtown San Francisco is littered with a dangerous mix of drug needles, garbage, and feces — an "unacceptable" condition that rivals some slums in developing countries, an NBC affiliate reported Thursday.

The investigation surveyed 153 blocks of the city – a more than 20-mile stretch that includes popular tourist spots like Union Square and major hotel chains, as well as City Hall, schools, playgrounds and a police station, NBC Bay Area reported.

The NBC affiliate said it spent three days on its survey, discovering trash on every one of the blocks surveyed. While some streets were littered with items as small as a candy wrapper, the vast majority of trash found included large heaps of garbage, food, and discarded junk.

The investigation also found 100 drug needles and more than 300 piles of feces throughout downtown, the outlet reported.

Dr. Lee Riley, an infectious disease expert at University of California, Berkeley, told the news outlet said the investigation's results shows parts of San Francisco might be dirtier than the slums in some developing countries.

"The contamination is . . . much greater than communities in Brazil or Kenya or India," he told the affiliate.

City supervisor Hillary Ronen called the findings "unacceptable" — and blamed the problem on a lack of funding to deal with the city's homeless population.

"We're losing conventions in San Francisco," she told the affiliate. "All of this is happening because we aren't addressing the root cause, which is we need more temporary beds for street homelessness."